Degassing device and degassing method for die-casting device

ABSTRACT

A degassing device configured to remove gas from a mold for die-casting, which includes a first path to inject molten metal into a cavity, a second path to remove gas from the cavity and a third path to measure the degree of the vacuum of the cavity. The degassing device incudes a first path opening/closing device connecting the first path and a vacuum device, a second path opening/closing device connecting the second path and the vacuum device and a controller capable of providing an actuation timing time lag between the actuation timings of the first path opening/closing device and the second path opening/closing device.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a U.S. National Stage application of International Application No. PCT/JP2019/009940, filed Mar. 12, 2019, the contents of which are hereby incorporated herein by reference.

BACKGROUND Field of the Invention

The present invention relates to a degassing device and a degassing method for a die-casting apparatus.

Background Information

When casting a die-cast product, a mold release agent is applied to a mold so that it is easier to remove the product from the mold. Also, a lubricant agent is applied to the mold to move the mold. When the mold release agent and the lubricant agent come into contact with hot molten metal, they burn and generate gas. It is known that this gas causes shrinkage cavities and the like in die-cast products and deteriorates the quality of die-cast products. Therefore, a conventional method has been adopted, in which air is sucked out from inside of a mold to improve the quality of die-cast products. This device to remove gas from a mold is a degassing device of a die-casting apparatus.

For example, Japanese Patent Application of Publication No. 2014-91159 discloses a device that prevents entrapment of gas in a molten metal supplied to a cavity of a mold of a die-casting apparatus, and a method for removing the gas.

SUMMARY

As can be understood, the method disclosed in Patent Application of Publication No. 2014-91159 removes gas from the vicinity of molten metal before being supplied to the inside of a mold. Thus, it has been found that with this method, it is difficult to remove air inside of the cavity. Therefore, it is submitted that the method does not sufficiently improve the quality of die-cast products.

The present invention has been made in view of the above-mentioned circumstances, and the purpose is to provide a degassing device of a die-casting apparatus and a degassing method for a die-casting apparatus, that improve the quality of die-cast products by reliably removing air from a cavity.

In order to achieve the above-mentioned purpose, a degassing device according to an embodiment of the present invention is a degassing device to remove gas from a mold for die-casting, including a first path through which molten metal is injected into a cavity, a second path through which gas is removed from the cavity and a third path in which the degree of vacuum of the cavity is measured. The degassing device includes a first path opening/closing device to connect the first path and a vacuum device, a second path opening/closing device to connect the second path and the vacuum device and a control device capable of providing an actuation timing time lag between the actuation timings of the first path opening/closing device and the second path opening/closing device.

For example, in the degassing device according to an embodiment of the present invention, the control device defines the difference between a first vacuum-reaching time obtained by measuring the degree of vacuum of the cavity from the third path when the first path opening/closing device is actuated and a second vacuum-reaching time obtained by measuring the degree of vacuum of the cavity from the third path when the second path opening/closing device is actuated, as the actuation timing time lag.

For example, the degassing device according to an embodiment of the present invention is provided with a vacuum suction groove inside of a sleeve, at a sleeve vacuum suction port for removing gas from the inside of the sleeve that is the first path and through which molten metal is injected into the mold. The length of the vacuum suction groove is shorter than the length of a sliding surface of a tip that pushes the molten metal inside of the sleeve and the width of the vacuum suction groove is one third or less of the inner diameter of the sleeve.

For example, a vacuum suction path closing device is further provided between the cavity and the second path opening/closing device and the cross-sectional area of the sleeve vacuum suction port is 1.5 to 2.0 times the minimum cross-sectional area of a path of the vacuum suction path closing device and the cross-sectional area of the vacuum section groove is 1.1 to 1.2 times the cross-sectional area of the sleeve vacuum suction port.

In order to achieve the above-mentioned purpose, a degassing method according to an embodiment of the present invention is a method to remove gas from the mold for die-casting, including the first path through which molten metal is injected into the cavity, the second path through which gas is removed from the cavity and the third path in which the degree of vacuum of the cavity is measured. The method includes a preceding process in which the first vacuum-reaching time obtained by measuring the degree of vacuum of the cavity, when the first path opening/closing device connecting the first path and the vacuum device of the degassing device, is actuated and the second vacuum-reaching time obtained by measuring the degree of vacuum of the cavity, when the second path opening/closing device connecting the second path and the vacuum device, is actuated, are compared and the difference thereof is used as the actuation timing time lag, and a degassing process in which the first or the second path opening/closing device having the longer vacuum-reaching time out of the first vacuum-reaching time and the second vacuum-reaching time, is actuated first and the second or the first path opening/closing device having the shorter vacuum-reaching time is actuated after the actuation timing time lag has past.

According to the present invention, it is possible to improve the quality of die-cast products by reliably removing air from a cavity.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be explained in more detail hereinafter with reference to the drawings.

FIG. 1 is a cross-sectional view of a degassing device, a mold and a sleeve according to Embodiment 1 of the present invention.

FIG. 2 is a plan view showing a cavity surface of a fixed mold used for the degassing device according to Embodiment 1.

FIG. 3 is a plan view showing a cavity surface of a movable mold used for the degassing device according to Embodiment 1.

FIG. 4 is a cross-sectional view of the sleeve used for the degassing device according to Embodiment 1.

FIG. 5 is a cross-sectional view of the sleeve used for the degassing device according to Embodiment 1, taken along line A-A (see FIG. 4).

FIG. 6 is a cross-sectional view of the sleeve used for the degassing device according to Embodiment 1.

FIG. 7 is a side view of a tip used for the sleeve which is used for the degassing device according to Embodiment 1.

FIG. 8 is a cross-sectional view of a vacuum suction path closing device of the degassing device according to Embodiment 1.

FIG. 9 is a schematic view of a vacuum control device of the degassing device according to Embodiment 1.

FIG. 10 is a figure showing the measurement result of degree of vacuum of the degassing device according to Embodiment 1.

DETAILED DESCRIPTION

Hereinafter, a degassing device of a die-casting apparatus and a method for degassing a die-casting apparatus according to an embodiment of the present invention will be described.

Embodiment 1

A degassing device 14 of a die-casting apparatus according to a first Embodiment of the present invention is shown in FIG. 1. The degassing device 14 is used to remove gas from inside of a cavity 9 of a mold 13 and a sleeve 3. The degassing device 14 is connected to the mold 13 and the sleeve 3. Also, a vacuum degree measuring device 18 shown in FIG. 9 measures the degree of vacuum of the cavity 9. The vacuum degree measuring device 18 is connected to the mold 13.

The mold 13 is used by combining a fixed mold 13A and a movable mold 13B. A surface that forms the cavity 9 on the fixed mold 13A is shown in FIG. 2. A surface that forms the cavity 9 on the movable mold 13B is shown in FIG. 3. Concave portions such as grooves formed on the surfaces of the respective molds are fitted together by combining the fixed mold 13A and the movable mold 13B, and thus, the cavity 9 and a runner 7 and a pouring gate 8, as an example of a first path, shown in FIG. 1, are formed inside of the mold 13. Additionally, as an example of a second path, a degassing gate 10 and a degassing groove 11 are formed. Furthermore, as an example of a third path shown in FIG. 9, a vacuum degree measuring groove 16 is formed.

As shown in FIG. 1, a vacuum suction path closing device 12 is connected to the degassing groove 11 and is arranged inside of the mold 13. As shown in FIG. 9, a vacuum degree measuring path closing device 17 is connected to the vacuum degree measuring groove 16 and is arranged inside of the mold 13.

As shown in FIG. 8, the vacuum suction path closing device 12 includes a fixed vacuum suction path closing device 12A arranged in the fixed mold 13A, a movable vacuum suction path closing device 12B arranged in the movable mold 13B and a vacuum suction path closing valve 12C. The vacuum suction path closing valve 12C is arranged inside of the fixed vacuum suction path closing device 12A and moves in the axial direction by air pressure to open and close the path between the degassing groove 11 and a cavity vacuum suction pipe.

As shown in FIG. 9, the vacuum degree measuring path closing device 17 includes a fixed vacuum degree measuring path closing device 17A arranged in the fixed mold 13A, a movable vacuum degree measuring path closing device 17B arranged in the movable mold 13B and a vacuum degree measuring path closing valve 17C. The vacuum degree measuring path closing valve 17C is arranged inside of the fixed vacuum degree measuring path closing device 17A and moves in the axial direction by air pressure to open and close the path between the vacuum degree measuring groove 16 and a vacuum pressure manometer 18A.

As shown in FIG. 1, the sleeve 3 has a cylindrical shape with flanges. With the flanges on the sleeve 3 as a reference, the outer perimeter of the shorter cylindrical portion is fitted into the hole made in the fixed mold 13A so that the axial direction is horizontal. The inside of the sleeve 3 is connected to the cavity 9 through the runner 7 and the pouring gate 8 that are connected from the hole. The longer cylindrical portion of the sleeve 3 protrudes from the mold 13. A molten metal supply port 2 for pouring a molten metal 4A into the sleeve 3, is opened near the end of the cylindrical portion protruding from the mold 13 of the sleeve 3. A tip 1 for pushing the molten metal 4A poured into the sleeve 3 into the mold 13, is inserted into the sleeve 3 from the protruding portion side of the sleeve 3. When the tip 1 is pushed into the cylinder of the sleeve 3 by the die-casting apparatus, the molten metal 4A inside of the cylinder is moved to the cavity 9 of the mold 13. A sleeve vacuum suction port 5 is opened in the upper part of the sleeve 3, that is closer to the mold 13 side than the molten metal supply port 2 in order to remove gas from inside of the sleeve 3. A groove is formed near the opening inside of the cylinder of the sleeve vacuum suction port 5. As shown in FIG. 5, the length of the groove in the width direction is a sleeve vacuum suction groove width L3 and the length of the sleeve 3 in the axial direction is a sleeve vacuum suction groove length L1, as shown in FIG. 6. As shown in FIG. 7, the length of a sliding surface of the tip 1 is a tip sliding surface length L2.

In this embodiment, the sleeve vacuum suction groove length L1 is smaller than the length L2 of the tip sliding surface 1A of the tip 1 shown in FIG. 7. The sleeve vacuum suction groove width L3 is one third or less of a tip diameter D of the tip 1 shown in FIG. 4.

In this embodiment, the cross-sectional area of the sleeve vacuum suction port 5 is 1.5 to 2 times of the minimum cross-sectional area of a path of the vacuum suction path closing device 12. It has been experimentally confirmed that this stabilizes the time for degassing the cavity 9. Also, the cross-sectional area of the sleeve vacuum suction groove 6 is 1.1 to 1.2 times of the cross-sectional area of the sleeve vacuum suction port 5. It has been experimentally confirmed that the levels of gas suctioning from the sleeve vacuum suction port 5 and from the sleeve vacuum suction groove 6 are leveled and degassing is performed efficiently.

As shown in FIG. 1, the degassing device 14 includes a vacuum tank 14A as an example of a vacuum device, a sleeve vacuum suction solenoid 14B as an example of a first path opening/closing device which is arranged directly adjacent to the vacuum tank 14 a and connected to the first path, a sleeve vacuum suction pipe 14C arranged immediately after the sleeve vacuum suction solenoid 14B, a sleeve vacuum suction filter 14D arranged immediately after the sleeve vacuum suction pipe 14C and a sleeve vacuum suction pipe 14E arranged on the path from the sleeve vacuum suction filter 14D to the sleeve vacuum suction port 5 of the sleeve 3. Additionally, the degassing device 14 includes a cavity vacuum suction solenoid 14F as an example of a second path opening/closing device which is arranged directly adjacent to the vacuum tank 14A and connected to the second path, a cavity vacuum suction pipe 14G arranged immediately after the cavity vacuum suction solenoid 14F, a cavity vacuum suction filter 14H arranged immediately after the cavity vacuum suction pipe 14G and a cavity vacuum suction pipe 141 arranged on the path from the cavity vacuum suction filter 14H to the vacuum suction path closing device 12.

Furthermore, the degassing device 14 includes a sleeve vacuum pipe cleaning solenoid 14J which operates to clean the sleeve vacuum suction filter 14D and the sleeve vacuum suction pipe 14E and a cavity vacuum pipe cleaning solenoid 14M which operates to clean the cavity vacuum suction filter 14H and the cavity vacuum suction pipe 141.

Additionally, the degassing device 14 includes a vacuum suction closing solenoid 12D which actuates the vacuum suction path closing valve 12C in the direction in which the path from the degassing groove 11 closes in order to operate the vacuum suction path closing device 12. Furthermore, the degassing device 14 includes a vacuum suction opening solenoid 12E which actuates the vacuum suction path closing valve 12C in the direction in which the path from the degassing groove 11 opens.

As shown in FIG. 9, the vacuum degree measuring device 18 includes the vacuum pressure manometer 18A connected to the third path, a vacuum control device (electronic controller) 18B which is a control device receiving a signal from the vacuum pressure manometer 18A and a vacuum degree measuring path cleaning solenoid 18C operates to clean the vacuum degree measuring path.

Additionally, the vacuum degree measuring device 18 includes a vacuum degree measuring path closing solenoid 17D which actuates the vacuum degree measuring path closing valve 17C in the direction in which the path from the vacuum degree measuring groove 16 closes in order to operate the vacuum degree measuring path closing device 17. Furthermore, the vacuum degree measuring device 18 includes a vacuum degree measuring path opening solenoid 17E which actuates the vacuum degree measuring path closing valve 17C in the direction in which the path from the vacuum degree measuring groove 16 opens.

Next, a method to remove gas from the cavity 9 of the mold 13 and the sleeve 3 by using the degassing device 14 according to an embodiment of the present invention will be described. First, as a preparation step, a preceding process of measuring the characteristics of the mold 13 will be explained.

The degassing device 14 has two paths that are a path for removing gas from the degassing groove 11 side of the mold 13 and a path for removing gas from the sleeve 3 side. Each path from the vacuum tank 14A to the cavity 9 has different pipe capacity and path resistance. Thus, even if the sleeve vacuum suction solenoid 14B and the cavity vacuum suction solenoid 14F are opened simultaneously, the times to actually start removing gas from the cavity 9 are different. In this embodiment, since the pipe capacity of the path for removing gas from the sleeve 3 side is larger, the timing to remove gas from the cavity 9 is delayed compared to the timing for removing gas from the degassing groove 11 side. That is, firstly, the gas is removed from the cavity 9 from the degassing groove 11 side, and then, after a predetermined time has passed, the gas is removed from the runner 7. Therefore, the gas existed in the cavity 9 once moves from the degassing gate 10 towards the degassing groove 11, then, returns to the cavity 9 and moves from the pouring gate 8 towards the runner 7. As a result, the time for removing gas from the cavity 9 is delayed. Then, degassing from the cavity 9 does not happen in time for die-casting cycle and the casting is performed in a state in which degassing is insufficient. As a result, defective casting such as shrinkage cavities can be caused and the quality of die-cast products is not improved.

Therefore, the timing of degassing from the cavity 9 through the two paths is set to be the same. As a result, the cavity 9 is sufficiently degassed to prevent defective casting such as shrinkage cavities and the quality of die-cast products is improved.

Therefore, how much the time lag in the timing for starting to remove gas from the cavity 9 is measured between the path to remove gas from the degassing groove 11 and the path to remove gas from the sleeve 3, when the sleeve vacuum suction solenoid 14B and the cavity vacuum suction solenoid 14F are actuated simultaneously. By providing a difference in the actuation timings of the sleeve vacuum suction solenoid 14B and the cavity vacuum suction solenoid 14F according to the time lag, the timings of removing gas from the cavity 9 are synchronized.

Next, a method will be explained, in which a time lag occurs between the path to remove gas from degassing groove 11 and the path to remove gas from the sleeve 3, when the sleeve vacuum suction solenoid 14B and the cavity vacuum suction solenoid 14F are opened simultaneously.

The die-casting apparatus (not shown) pushes the tip 1 inserted into the sleeve 3 to reach a position where a position signal A is emitted, that is, a position where the tip 1 caulks the molten metal supply port 2. Then, the sleeve vacuum suction solenoid 14B is actuated. As a result, the path between the vacuum tank 14A and the cavity 9 is connected and gas is removed from inside of the sleeve 3, the runner 7 and the cavity 9. A vacuum degree measuring device 18 is coupled to the cavity 9. The vacuum degree measuring path opening solenoid 17E is actuated to couple the cavity 9 with the vacuum pressure manometer 18A. Starting from the timing when the sleeve vacuum suction solenoid 14B is turned ON, a first vacuum-reaching time in which the vacuum pressure manometer 18A starts to operate, is measured. The first vacuum-reaching time is defined as T1.

Next, the time for removing gas from the degassing groove 11 side is measured. The cavity vacuum suction solenoid 14F is actuated while the tip 1 stays at the position where the position signal A is emitted. Further, the vacuum suction opening solenoid 12E is actuated to move the vacuum suction path closing valve 12C. As a result, the path between the vacuum tank 14A and the cavity 9 is connected and the gas is removed from the degassing groove 11 and the cavity 9. The vacuum degree measuring device 18 is connected to the cavity 9. The vacuum degree measuring path opening solenoid 17E is actuated to couple the cavity 9 with the vacuum pressure manometer 18A. Starting from the timing when the cavity vacuum suction solenoid 14F is turned ON. a second vacuum-reaching time in which the vacuum pressure manometer 18A starts to operate, is measured. The second vacuum-reaching time is defined as T2.

In this embodiment, as mentioned above, T1 is larger than T2. Then, the value of T1-T2, which is the difference, is set as the actuation timing time lag T. That is, the cavity vacuum suction solenoid 14F is actuated after the sleeve vacuum suction solenoid 14B is actuated and the actuation timing time lag T has passed. In this way, the timings for removing gas from the cavity 9 will be the same between the path to remove gas from the degassing groove 11 side and the path to remove gas from the sleeve 3 side. As a result, the gas inside of the cavity 9 does not move unnecessarily, and it is possible to sufficiently remove gas from the cavity 9 and the degree of vacuum inside of the cavity 9 is improved.

FIG. 10 shows how the degree of vacuum of the cavity 9 changes between the situation in which a time lag in the timing of removing gas from cavity 9 exists and the situation in which the time lag does not exist. TIME on the abscissa axis represents a time lapse and the ordinate axis represents the degree of vacuum. NOT PROPER VACUUM LINE represents the situation in which a time lag in the timing of removing gas from cavity 9 exists and PROPER VACUUM LINE represents the case in which the time lag in the timing of removing gas from cavity 9 does not exist. The difference in the timing for degassing the cavity 9 is DELAY which represents the delay in vacuuming. In a cycle of casting process of a die-casting apparatus, the time to COMPLETE INJECTION, which represents the completion of filling from the start of HIGH SPEED INJECTION, which represents a high-speed injection, does not change. Therefore, when a DELAY which represents the delay in vacuuming exists, the degree of vacuum to be reached is insufficient, as shown in NOT PROPER VACUUM LINE. As a result, the degassing of the cavity 9 is insufficient and defective casting such as shrinkage cavities can be caused and the quality of die-cast products is not improved.

Next, the casting process of the die-casting apparatus will be explained, using the actuation timing time lag T obtained in the above-mentioned preparation step.

Initial Position

A state showing the initial position of the die-casting apparatus is shown in FIG. 1. At this point, appropriate amount of molten metal 4A for casting is poured into of the sleeve 3 from the molten metal supply port 2.

First Position

Next, the tip 1 is pushed into the sleeve 3 and reaches the position where the position signal A is emitted, as shown in FIG. 4.

At this moment, the molten metal supply port 2 is caulked by the tip 1 and air does not leak out from the molten metal supply port 2.

The water level of molten metal 4A is raised by being pushed by the tip 1. The space where the molten metal 4A does not exist inside of the sleeve 3 is defined as a sleeve space 3A, at this moment.

When the position signal A is emitted, the vacuum control device 18B actuates the sleeve vacuum suction solenoid 14B and the gas inside of the sleeve 3 is removed.

After the actuation timing time lag T has passed, the vacuum control device 18B actuates the cavity vacuum suction solenoid 14F and the vacuum suction opening solenoid 12E and the gas is removed from the degassing groove 11 side.

Then, the tip 1 is pushed into the sleeve 3 at a relatively low speed.

Second Position

The tip 1 is further pushed into the sleeve 3 and reaches the position where a position signal B is emitted, as shown in FIG. 6.

At this moment, the sleeve vacuum suction port 5 is caulked by the tip 1 and air does not leak out from the sleeve vacuum suction port 5.

Since the molten metal 4A is further pushed by the tip 1, the water level is raised, and it is in the state of molten metal 4B. The space where the molten metal 4B does not exist inside of the sleeve 3 is defined as a sleeve space 3B, at this moment.

When the position signal B is emitted, the vacuum control device 18B actuates the sleeve vacuum suction solenoid 14B and degassing from the sleeve 3 is stopped. Additionally. the vacuum control device 18B actuates the cavity vacuum suction solenoid 14F and the vacuum suction opening solenoid 12E and degassing from the degassing groove 11 side is stopped. At this moment. degassing supposed to be stopped before the molten metal 4B reaches the runner 7. The cavity 9 is degassed from the inside and a vacuum.

Then, the tip 1 is pushed into the sleeve 3 at a relatively high speed.

Third Position

When the tip 1 is pushed all the way into the sleeve 3, the molten metal 4B inside of the sleeve 3 is sent into the vacuumed cavity 9, and then, cooled and solidified inside of the mold 13.

The above is one cycle of casting by the die-casting apparatus.

In this embodiment, degassing of cavity 9 is simultaneously performed with the timing of removing gas of the cavity 9 from the degassing groove 11 side and the timing of removing gas of the cavity 9 from the sleeve 3 side by providing the actuation timing time lag T between the actuation timings of the sleeve vacuum suction solenoid 14B and the cavity vacuum suction solenoid 14F that connects the respective path to the vacuum tank 14A. Therefore, the degree of vacuum of the cavity 9 is increased before the molten metal reaches the cavity 9 to prevent defective casting such as shrinkage cavities and a like and the quality of die-cast products is improved.

As results of experiments, it is confirmed that the degree of vacuum of the cavity 9 is more than twice as high as that in the method of removing gas only from a sleeve as in the invention disclosed in Patent Application of Publication No. 2014-91159. As a result, it is confirmed that an incidence of defective casting becomes half or less.

The present invention allows for various embodiments and modifications without deviating from the broad mind and scope of the present invention. Additionally, the above-mentioned embodiment is to explain the present invention and not to limit the scope of the present invention. That is, the scope of the present invention is described by the scope of claims and not by the embodiment. Various modifications made within the scope of the claims and the equivalent meaning of the invention are considered to be within the scope of the present invention. 

1. (canceled)
 2. A degassing device configured to remove gas from a mold for die-casting, which includes a first path to inject molten metal into a cavity, a second path to remove gas from the cavity and a third path to measure a degree of vacuum of the cavity, comprising: a first path opening/losing device configured to connect the first path and a vacuum device and a second path opening/closing device configured to connect the second path and the vacuum device; and an electronic controller capable of providing an actuation timing time lag between actuation timings of the first path opening/closing device and the second path opening/closing device; the electronic controller defining a difference between a first vacuum-reaching time obtained by measuring the degree of vacuum of the cavity from the third path when the first path opening/closing device is actuated and a second vacuum-reaching time obtained by measuring the degree of vacuum of the cavity from the third path when the second path opening/closing device is actuated, as the actuation timing time lag.
 3. (canceled)
 4. (canceled)
 5. A degassing method for removing gas from a mold for die-casting, which includes a first path to inject molten metal into a cavity, a second path to remove gas from the cavity and a third path to measure a degree of vacuum of the cavity, the method comprising: obtaining a first vacuum-reaching time by measuring the degree of vacuum of the cavity, when a first path opening/closing device connecting the first path and vacuum device of a degassing device, is actuated and a second vacuum-reaching time obtained by measuring the degree of vacuum of the cavity, when a second path opening/closing device connecting the second path and the vacuum device, is actuated, comparing and determining a difference thereof to use as an actuation timing time lag; and degassing by actuating the first path opening/closing device or the second path opening/closing device-first based on whether the first vacuum-reaching time and the second vacuum-reaching time is longer, and actuating the second path opening/closing device or the first path opening/closing device based on whether the second vacuum-reaching time or the first vacuum-reaching time is shorter after the actuation timing time lag has past. 